> air allows mines to use a very interesting way to communicate
This is a very important point to remember about subterranean tunnel systems. It is exactly what came to my mind when I watched the Boring Company video about a huge network of 3D tunnels.[1] The tech press, which had probably never even covered a construction project yet alone tunnels, was basically like "what about earthquakes"? But tunnel collapse is not the primary safety issue.
It's fires. Smoke and toxic gases from fires spread very quickly through tunnels.
I am a huge fan of the concept, by the way, but I want to emphasize that most fatalities from traffic tunnels have been from fires (apart from ordinary traffic accidents).[2][3][4][5] And Elon Musk has stated that what makes this vision feasible from a cost perspective is smaller tunnel diameters. Which makes air "communication" all the more accelerated and safety critical. Thus any vision of tunneling without detailing fire safety, evacuation systems and firefighter access is significantly incomplete, as these can add significant cost and fundamentally constrain designs.
> Smoke and toxic gases from fires spread very quickly through tunnels
It's not just the confined-space aspect that causes the fire gases to have such high lethality (although it's certainly extremely significant), it's also the rate of gas production.
Most solids and liquids don't actually burn; they emit flammable gases when exposed to heat, and it's those gases which actually undergo combustion. These gases are created by endothermic processes (pyrolysis and evaporation), and the more heat is available to convert unreactive solid/liquid combustibles into reactive gases, the faster the fire will burn. Therefore, less heat loss (to the outside environment or to non-combustibles) will enable a higher combustion rate and the fire will produce more heat.
Tunnels are quite good at retaining heat, so most of the heat produced by a fire will feed back right into heating combustibles -- enabling devastating heat release rates in the tens to hundreds of megawatts. The heat release rate is roughly proportional to the fire's fuel consumption rate; which will be roughly proportional to the rate of lethal gas (CO/HCN/CO2) production and oxygen depletion.
The radiant heat flux alone can make the fire unapproachable by even appropriately-equipped firefighters -- the massive production of superheated, oxygen depleted, CO/HCN-containing gases can kill -- far beyond the range that the heat flux is deadly.
Great points. An interesting addition is that Musk has also stated that the tunnels would be vacuums (to 5-6 atmospheres) in order to seal against the water table.[1] It's interesting to consider the impacts on fire safety, both in the reduction of risk of spread (a positive) and the difficulties it presents with evacuation from compromised vehicles (a negative).
Can't watch the video now, but are you saying they are vacuums or pressurized? If they are vacuums, the highest vacuum you can have is -1 atmosphere, I.e. No air.
5-6 atmospheres would be PRESSURIZED, not vacuum.
Also, a vacuum would pull in water from the water table, you'd need pressure to keep it out.
Vacuum would be good for fire prevention, things can't burn if there's no oxygen. Pressure, on the other hand, will greatly amplify fire, if you just pressurize air. If you want to avoid that, you have to pressurize with a neutral gas like nitrogen, which would be expensive if there is any regular amount of gas leakage.
In either case, you'd have to build compartments that were pressure/vacuum proof (think a submarine or spacecraft) -- and in either case, leaving the pressure vessel would pose dire risks to occupants.
I'll try to watch the video when I'm back on WiFi.
From the transcript, this is what the "5 atmospheres" thing meant -- it was about the pressure differential, and that whether the inside is at 1 atm or 0 atm isn't a big deal if the tunnel has to be underground (in which case it already has to stand quite a bit of outside pressure!):
> Exactly. And looking at tunneling technology, it turns out that in order to make a tunnel, you have to — In order to seal against the water table, you've got to typically design a tunnel wall to be good to about five or six atmospheres. So to go to vacuum is only one atmosphere, or near-vacuum. So actually, it sort of turns out that automatically, if you build a tunnel that is good enough to resist the water table, it is automatically capable of holding vacuum.
Thank you for clarifying. I misspoke earlier slightly, but the result is the same: when you build a tunnel strong enough to withstand the water table, it can hold a near vacuum. This helps transport and energy efficiency.. but also presents interesting issues for fire safety.
Sure, but it's -1 atm gradient, which is how we commonly measure pressure. I.e., when you fill your car tires to 32 psi, that's 32 psi over atmospheric. When you're talking about pressure, it's the gradient that matters.
It was taught as psia, -g, & -d (or absolute, gauge, and differential) when I was in school, so I read your -1 atm as psid. Your car example would be 32 psi gauge assuming STP, or ~36 psi absolute.
The miners are below the surface and not at 1 atm, so any gauge measures taken there would be psid.
From the Wikipedia page of the Mont Blanc tunnel fire:
"Some victims escaped to the fire cubicles. The original fire doors on the cubicles were rated to survive for two hours. Some had been upgraded in the 34 years since the tunnel was built to survive for four hours. The fire burned for 53 hours and reached temperatures of 1,000 °C (1,830 °F), mainly because of the margarine load in the trailer, equivalent to a 23,000-litre (5,100 imp gal; 6,100 US gal) oil tanker, which spread to other cargo vehicles nearby that also carried combustible loads."
It was days before the tunnel cooled enough for recovery crews to enter.
With this sort of heat release rate and amount of combustible material, fire doors alone are useless. Even if the fire doors miraculously remain intact and gastight, the walls and doors will eventually conduct enough heat to make the temperature in the fire refuges untenable for human life.
100 years ago, yesterday, was the worst hard rock mining disaster in the US, in Butte, Montana. They didn't have this way of warning the miners back then and 168 miners died due to a fire in one of the shafts. Most died from asphyxia.
Michael Punke, the author of the Revenant, wrote an excellent non-fiction book about it called "Fire and Brimstone: The North Butte Mining Disaster of 1917".
It should clearly (or likely) be the other way around, at least in any country with a left-to-right reading order, OCD or not :)
We scan information faster in the preferred reading direction, and flipping the warning gas on half a second earlier will likely, sooner or later save somebody from harm. Not that there aren't other ways to improve safety in mines, but each small part counts, I guess?
Just reading about that article triggered an olfactory memory of the related compound 2-mercaptoethanol (or beta-mercaptoethanol as it was labeled in the lab). Used to reduce disulfide links in proteins (edit: see more correct response below) so that they would unravel a bit and separate by size more as they travel through the western blot matrix.
Unlike carbon monoxide this compound had a very "this will kill you" smell to it.
2ME is the "gas leak" additive that gets put into gasoline.
It smells like sulfur + burnt rice crackers to me... It's actually not that dangerous of a compound - I've spilled it on myself gloveless and it's not a big deal.
Also a bit of a possibly overpedantic note - you can run gels without reducing the disulfide bonds, but typically those proteins will run through the gel faster, not slower because of a more compact form. Because not all proteins have disulfides, if you reduce them first, it creates a predictable relationship between the protein size and the migration velocity, which is the desirable property, not speed.
Context matters - I worked in a surface science lab, so lots of gold monolayers being made with sulfur compounds. While I wouldn't say they're remotely pleasant, I'm so used to them that it's more like a gradient where you're like "this could be worse". Pure chemicals are well...pure. It's when it smells like uncontrolled biology that I get uncomfortable.
is that the nasty sour smelling chemical? sort of like sulfur, vinegar, burnt gunpowder, and vodka, mixed together? i used to get a whiff of it at my dad's bench at his workplace.
Acetic acid and Butyric acid. Used for those clear tool handles. [1][2] It gets nastier once you realize you are smelling the odor of vomit with hints of vinegar.
Maybe. To me it had a very "industrial-fish" smell is the best way I can put it. Not fishy like Thai fish oil, but maybe like an ocean oil spill site puréed, baked in the sun and concentrated? I remember it provoked a visceral reaction to not smell it more.
Whenever a big event happens, like some big e2 celebrity dies, there's a surge of people logging into the site to pay their respects. Weddings and funerals, they say, but for e2 it seems to be only funerals.
If our noses were "sharper", i.e., able to distinguish on a deeper more meaningful level like a dog, could we transmit complex information with olfactory encoding?
Right now the smells are simple signals; I'm curious if a scent could be engineered to contain a language. Like paper and writing.
I'm asking for my story, in which sapient rats struggle against two-legged monsters with opposable thumbs.
I've wondered if one could build a device that outputs different combinations of distinct scents for training dogs. Like condition the dog to understand "sit" = "bacon smell" and "shake" = "cat". My theory was that dogs have more cognitive resources dedicated to processing olfactory information and so they could also be trained to understand and perform more complex tasks. Like, "bacon + cat + shoe smell" = "bark while running left"
I wonder if we could tie this to Jenkins for when a build breaks. Would make for a nicer alternative than sirens and flashing lights, although I suspect people would tend to clear the office...
I instinctively hovered my mouse over the link to wintergreen, my brain fully expecting to click and experience the smell - as I would with any image, video, or sound. Took me a few seconds to manage expectations!
"Employees of the Union Oil Company of California reported first in 1938 that turkey vultures would gather at the site of any gas leak. After finding that this was caused by traces of ethanethiol in the gas it was decided to boost the amount of ethanethiol in the gas, to make detections of leaks easier"
I remember seeing this for sale on BOC's website when looking for CO2 a while back (https://www.boc.co.nz/shop/en/nz/stench-gas). I briefly considered buying some for nefarious purposes, but I think I figured that they probably wouldn't just sell it to any random person.
Reminds me of the Friends' episode where Ross goes on and on with the (bored and weirded out) pizza delivery girl about the smelly chemical added to natural gas in order to make it olfactible & safer to use.
I think my family went to that exhibit while I was pre adolescent. I got scared so only my mother & sister went, while I stayed topside with my father. We window shopped the souvenir shop
Nowadays my sister suffers claustrophobia & I feel most comfortable shoved into small crooks. But I think I was mostly offset by anxiety related to ventilation
Visited Timmins this May, another northern Ontario city. It was snowing
This is a very important point to remember about subterranean tunnel systems. It is exactly what came to my mind when I watched the Boring Company video about a huge network of 3D tunnels.[1] The tech press, which had probably never even covered a construction project yet alone tunnels, was basically like "what about earthquakes"? But tunnel collapse is not the primary safety issue.
It's fires. Smoke and toxic gases from fires spread very quickly through tunnels.
I am a huge fan of the concept, by the way, but I want to emphasize that most fatalities from traffic tunnels have been from fires (apart from ordinary traffic accidents).[2][3][4][5] And Elon Musk has stated that what makes this vision feasible from a cost perspective is smaller tunnel diameters. Which makes air "communication" all the more accelerated and safety critical. Thus any vision of tunneling without detailing fire safety, evacuation systems and firefighter access is significantly incomplete, as these can add significant cost and fundamentally constrain designs.
[1] https://www.youtube.com/watch?v=u5V_VzRrSBI
[2] https://en.wikipedia.org/wiki/Caldecott_Tunnel_fire
[3] https://en.wikipedia.org/wiki/Gotthard_Road_Tunnel#2001_coll...
[4] https://en.wikipedia.org/wiki/Kaprun_disaster
[5] https://en.wikipedia.org/wiki/Mont_Blanc_Tunnel#1999_fire